1. Field of the Invention
This invention relates to a method for manufacturing a self-locking spring nut, and more particularly to a self-locking spring nut which may be locked on a bolt elastically.
2. Description of the prior art
In a combination of a female thread and a male thread, such as for instance, those of a nut and a bolt, there should be provided a clearance between the male thread and the female thread, even in the case of a close-tolerance bolt and nut, for insuring smooth threading of the former into the latter. It follows from this that when tightening a nut on a bolt, the aforesaid clearance reduces a frictional force created between a female thread and a male thread, thus leading, more or less, to a loose joint.
Many attempts have been proposed to prevent such a loose joint by providing a lock nut or self-locking nut. These nuts may be classified into two types, i.e., single nut type and a double nut type.
Included by a single nut type are: (1) a nut which is deformed by a press machine; (2) a nut having an elliptic collar; (3) a nut, one end of which is to be deformed due to a tightening force; (4) a nut having a tongue for use in locking; (5) a nut having a resilient material such as nyron interposed between the bolt and the nut; (6) a nut which is used in combination with a washer. However, these attempts have suffered from disadvantages in that a tightening force varies as the time goes on, and there results a loose joint particularly in the presence of repeated vibrations. If the case comes to the worst, the threads are worn or damaged, and hence these nuts can no longer used again.